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### Systems at equilibrium

Posted: Wed Jan 29, 2020 12:13 pm
How does the concept of equilibrium apply to these systems in thermodynamics? I think Dr. Lavelle mentioned something about fluctuating volume and work stuff and if the external pressure exerted on the piston system thingy is constant then we can use one particular equation to calculate the work done?
I'm generally very lost. What does external pressure have to do with anything?

### Re: Systems at equilibrium

Posted: Wed Jan 29, 2020 12:28 pm
We will discuss it more when we start talking about thermodynamics. For now, all we need to know is that there is a difference in the amount of work done depending on whether the gaseous system is under pressure or not.

### Re: Systems at equilibrium

Posted: Wed Jan 29, 2020 12:56 pm
Angela Patel 2J wrote:We will discuss it more when we start talking about thermodynamics. For now, all we need to know is that there is a difference in the amount of work done depending on whether the gaseous system is under pressure or not.

what is this difference? Is this just a concept we have to know or are their formulas to demonstrate this.

### Re: Systems at equilibrium

Posted: Wed Jan 29, 2020 10:11 pm
In chapter 4A of the book we learn about reversible processes. I think we're going to discuss it in class later on but what I gathered from lecture today and from the reading is that when the system is at equilibrium and stable, it is reversible.

A reversible process is one where the tiniest change in any variable (tiniest stray from equilibrium) results in work being done. Tiniest here means infinitismal which is why we used integrals in class today. But an example is if all things are at equilibrium, the tiniest increase in the pressure of the system will result in work being done by the system on the surroundings.

As far as external pressure, if the external pressure is far larger than the pressure within the system then the tiny change in a variable will result in negligible work being done because the difference is so great. This means that it's not a reversible process.

Overall, don't worry. We'll prob cover it soon.